VOIP Network Readiness Assessment Software/Tools Recommendation

Use tracert from a dos prompt and look at the number of hops and the associated times. Your link to your ISP will need to be considered.

I'm actually looking for an off the shelf tool that simulates VOIP traffic and can give a MOS type score and possbile problems/solutions.

The local network will never be a problem. Its usually so high bandwidth that voip traffic will always get all the bandwidth that it requires. The only exception to this can be if voip and data is going down a single network cable to the phone and then onto the pc. Even then windows is so inefficient at transferring files you can only get an issue if you are transferring large files in another way.
Implementing QOS on your switches easily solves this problem though.

Transfering data over the internet is often the problem. You can configure QOS to control the upstream data but you have very little control over the downstream. The best way it to dedicate a 2nd internet connection for VoIP.

You then just need to make sure there is a good connection between you and the voip provider you intend to use. You can use a program called MTR (WinMTR under windows) to perform a traceroute but ping every hop with at least 1000 packets. You need a packet loss of practically 0 and certenly less than 1%.